History tidbit

[Edward Sharpe]

I have one of the Federal MacKay recvr's
It is a more modern version of my ip500 that has a triple crystal
detector on it from ww I era!
I have not seen one of the 1940's emer. 500 kc xtal rcvrs though..scan a
pic and email it !

thanks Ed Sharpe

3
Jeffrey Herman wrote:

> While on my way to the QA's (mathematics research texts in the
> library) I always find myself somehow taking a detour through
> the VK's (maritime radio) (how does that happen?). Anyway,
> I stumbled across a gem: 1944 edition of "Marine Radio Manual"
> (wartime edition).
>
> There are goodies in here I've never seen before ("How to test
> your Mackay and RMCA Auto Alarm receivers"). But here's a *real*
> curious item: From the FCC/ITU regulations:
> "CRYSTAL RECTIFIER. Whenever a vessel is subject to the Safety Con-
> vention, the radio installation, in addition to all other
> requirements,
> shall be provided with a radio receiver capable of receiving radio-
> telegraphy signals, A2 and B emissions, on all frequencies within
> the band 350 to 515 kcs by means of a crystal rectifier, and for this
> purpose such receiver shall not require the use of electron tube(s).
> The crystal rectifier may be included in the main receiver, in the
> emergency receiver, or an additional receiver having this facility
> may be provided which shall be located as near the emergency operating
>
> position as is practicable."
>
> First, don't be surprised to see the B-emission requirement, for
> it wasn't until *1965* that spark was finally outlawed on 500 kc
> for all (including distress) communications (see Schroeder's
> "Contact At Sea"). But my goodness, requiring a tubeless crystal
> rectifier onboard as late as 1944?
>
> Has anyone ever seen such a commercially-made rcvr for that band
> (350-515 kcs)?
>
> Stay tuned for more tidbits.
>
> Jeff KH2PZ / KH6 (student of maritime wireless)
>
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